1. Field of the Invention
The present invention relates to an auto-focusing method in a camera device, and more particularly, to an auto-focusing method that performs auto tracking of a moving object within a predetermined image in a camera module mounted onto a mobile communications device, such as a cellular phone, and provides continuous tracking of the moving object even when the moving object disappears from the image and subsequently reappears.
2. Description of the Related Art
In general, compact camera modules (CCMs) are small-sized and have been used in various kinds of IT applications such as toy cameras and portable mobile communications devices including camera phones, PDAs and smartphones. An increasing number of devices, mounted with small camera modules, have been released to satisfy consumer demand.
These camera modules that use image sensors, such as CCD or CMOS sensors, as main components are being manufactured. An image of an object is collected through an image sensor, and the collected image is stored as data in memory of the camera module. The stored data is displayed as an image through an LCD of the camera module or a display device such as a PC monitor.
Recently, auto-focusing technology has been widely used. According to auto-focusing technology, a subject is detected using a luminance signal of the subject that is captured through a camera lens, and an optical system is driven according to the detected subject to obtain focus on the subject.
According to autofocus via contrast detection, not every single subject within a photographing range of a camera necessarily becomes a target for auto-focusing, and a subject of interest within the photographing range generally becomes a target for auto-focusing. Auto-focusing based on contrast detection limits a target for auto-focusing to a subject within a partial range by extracting an image signal within an auto-focusing range among incoming image signals within the entire photographing range of an image sensor, and controlling focus so that the extracted image signal has the highest contrast.
However, as for auto-focusing using the current technology, when a subject moves within a predetermined image and is finally separated from an area of the image (for example, when the subject moves out of the image and disappears from the image), in the related art, existing information about the subject being tracked is lost, and thus it is no longer possible to track the subject.
In addition, in auto-focusing based on contrast detection according to the related art, an image may be unfocused while a lens position changes in order to find an optimal lens position at which a focused image is generated. In this case, it is more likely to fail to track a moving object of interest.
Meanwhile, when actual photographing is carried out, one subject is not always a target for auto-focusing, and a target for auto-focusing may need to be instantly shifted from one subject to another subject according to a user's judgement. Here, when it comes to setting a region of interest according to a user's input using a trackball or the like, the above target shift may cause problems with making a quick tracking response to the moving object.
In addition, DSC cameras currently being used provide moving object tracking ability. However, separate algorithms are required for the application to small devices including mobile phones due to hardware limitations such as memory.